Prepreg, inorganic fiber composite material containing the same, and method for manufacturing inorganic fiber composite material

Abstract

The present invention relates to a prepreg produced by mixing inorganic fibers and thermoplastic fibers to manufacture an inorganic fiber wet nonwoven fabric, thereby simplifying the process steps and improving productivity; an inorganic fiber composite material containing the same; and a method for producing an inorganic fiber composite material.

Description

[Technical Field]

[0001] This invention relates to a prepreg, an inorganic fiber composite material containing the same, and a method for manufacturing an inorganic fiber composite material, and by simplifying the process during the production of thermoplastic prepregs, high productivity and economic efficiency can be expected. [Background technology]

[0002] Fiber-reinforced composite materials are manufactured using fibers such as glass fibers, carbon fibers, aramid fibers, and silicon carbide fibers as reinforcing materials. Because they have lower density and higher strength compared to metallic materials, they have recently been applied to a wide range of fields.

[0003] Furthermore, with the recent rise of environmental concerns, there has been an increase in research aimed at recovering and reusing fibers from fiber-reinforced composite materials that are discarded after use, and the related market is also growing in size.

[0004] Methods for producing fiber-reinforced composite materials using such composite material fibers and recycled fibers include mixing the fibers with resin in the form of woven fabric, nonwoven fabric, or short fibers to create the composite material. In particular, when using recycled fibers, there are limitations to the production of composite materials, and in order to overcome these limitations, it is necessary to produce nonwoven fabric and then create the composite material.

[0005] Furthermore, prepregs, which are produced to manufacture fiber composite materials, are manufactured through processes such as solution impregnation and hot melt processes, and the manufactured prepregs are used to mold the fiber composite material into the desired shape. The process of manufacturing such thermosetting or thermoplastic prepregs involves complex procedures with various stages.

[0006] For example, the process includes steps such as unwinding the fibers, supplying a thermoplastic or thermosetting film, melting the supplied carbon fibers and film, impregnating them, and cooling the molten resin.

[0007] Therefore, such complex processes increase manufacturing time and costs, so it is necessary to simplify the process steps and improve productivity. In addition, it is necessary to develop materials with improved performance (e.g., strength, lightweight, electromagnetic wave shielding ability, etc.).

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] Therefore, an object of the present invention is to provide a prepreg that manufactures an inorganic fiber wet nonwoven fabric by mixing inorganic fibers and thermoplastic fibers, thereby forming a prepreg to simplify the process steps and improve productivity, an inorganic fiber composite material including the same, and a method for manufacturing an inorganic fiber composite material.

[0010] Another object is to provide a prepreg having improved performance (e.g., strength, lightweight, electromagnetic wave shielding ability, etc.) and an inorganic fiber composite material including the same.

[0011] However, the problems to be solved by the present application are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

Means for Solving the Problems

[0012] One aspect of the present application includes a step of manufacturing an inorganic fiber wet nonwoven fabric by mixing inorganic fibers and thermoplastic fibers, and a step of drying the inorganic fiber wet nonwoven fabric to manufacture a prepreg. A method for manufacturing an inorganic fiber composite material is provided.

[0013] ​​​3 The following provides a prepreg.

[0014] Still another aspect of the present application provides an inorganic fiber composite material including the prepreg. provides an inorganic fiber composite material.

Advantages of the Invention

[0015] The prepreg according to the present invention, the inorganic fiber composite material including the same, and the method for manufacturing the inorganic fiber composite material mix inorganic fibers and thermoplastic fibers to produce an inorganic fiber wet nonwoven fabric, thereby forming a prepreg to simplify the process steps, and it is possible to expect effects such as reduction of energy consumption and operating costs, improvement of space use efficiency of process equipment, and improvement of productivity.

[0016] In addition, there is an effect of improving the performance (for example, strength, light weight, electromagnetic wave shielding ability, etc.) of the prepreg and the inorganic fiber composite material including the same.

Modes for Carrying Out the Invention

[0017] Hereinafter, the actions and effects of the invention will be described in more detail through specific examples of the invention. However, such examples are merely presented as examples of the invention, and the scope of the invention is not defined thereby.

[0018] Prior to this, the terms and words used in this specification and the claims should not be construed as being limited to their ordinary or dictionary meanings. In accordance with the principle that the inventor can appropriately define the concept of the terms in order to explain his invention in the best way, they should be construed in a meaning and concept consistent with the technical idea of the present invention.

[0019] Therefore, it should be understood that the configurations of the examples described in this specification are merely one of the most preferred examples of the present invention and do not represent all of the technical ideas of the present invention. At the time of filing this application, there can be various equivalents and modifications that can replace these.

[0020] In this specification, singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as “includes,” “equip,” or “possess” are intended to specify the existence of implemented features, figures, stages, components, or combinations thereof, and should be understood not to preemptively exclude the possibility of the existence or addition of one or more other features, figures, stages, components, or combinations thereof.

[0021] In this specification, the terms "from" and "~" in "a to b" and "a~b" which indicate a numerical range are defined as ≥ a and ≤ b.

[0022] A method for producing an inorganic fiber composite material according to one aspect of the present invention comprises the steps of mixing inorganic fibers and thermoplastic fibers to produce an inorganic fiber wet nonwoven fabric, The step may include drying the inorganic fiber wet nonwoven fabric to produce a prepreg.

[0023] In one embodiment, the step of mixing inorganic fibers and thermoplastic fibers to produce an inorganic fiber wet nonwoven fabric may include: a first step of adding inorganic fibers, thermoplastic fibers, and a wetting agent to a solvent and stirring to produce a solution containing hydrophilized inorganic fibers; a second step of adding a copolymer solution to the solution containing the hydrophilized inorganic fibers to disperse the hydrophilized inorganic fibers and produce an inorganic fiber dispersion; and a third step of molding the inorganic fiber dispersion.

[0024] Furthermore, the copolymer may include acrylic acid-based monomer units and acrylamide-based monomer units.

[0025] Water can be used as the solvent.

[0026] The copolymer may be random or block copolymer depending on the synthesis process.

[0027] The first step may also be a step of introducing hydrophilic groups capable of forming hydrogen bonds with water on the surface of the hydrophobic inorganic fiber to enable water dispersion.

[0028] Furthermore, the second step is a step to induce the dispersion of the inorganic fibers by electrostatic repulsion and at the same time prevent the re-aggregation of the inorganic fibers by utilizing steric hindrance. The copolymer solution obtained by dissolving the copolymer in a solvent is mixed with the inorganic fibers that have been properly hydrophilized in the first step, and a certain amount of solvent can be added to ensure proper dispersion.

[0029] For example, in the second step, the solution containing the hydrophilized inorganic fibers prepared in the first step (which may include inorganic fibers, thermoplastic fibers, solvent, wetting agent, binder, etc.) can be mixed with the copolymer solution (polymer (dispersant) and a solvent (e.g., water)) in an amount of 1 to 50 times the weight of the inorganic fibers.

[0030] On the other hand, the inorganic fibers can be selected and used from carbon fibers, glass fibers, ceramic fibers, metal fibers, basalt fibers, recycled carbon fiber, recycled glass fiber, etc., recycled from prepregs by chemical / physical methods, or a combination thereof.

[0031] In one embodiment, binder fibers or binder polymers may be added in the first step.

[0032] The aforementioned binder fibers or binder polymers are used to increase the bonding strength of the inorganic fiber wet nonwoven fabric after the drying step during the production of the inorganic fiber wet nonwoven fabric, and may be, for example, polyvinyl alcohol (PVA) fibers, low-melting-point polyester (LMPET) fibers, or polyvinyl alcohol resin.

[0033] In one embodiment, in the first step, a shear force can be applied and the mixture stirred at a speed of 100 to 2,000 rpm for one minute or more. This is to minimize damage to the fibers contained in the inorganic fiber dispersion, and devices capable of applying high shear force, such as a pulper, overhead stirrer, or knife beater, can be used.

[0034] In the first step, the stirring speed may be, for example, 100 rpm to 1,000 rpm, 200 rpm to 2,000 rpm, 200 rpm to 1,500 rpm, 300 rpm to 1,600 rpm, 500 rpm to 1,500 rpm, or 1,250 rpm.

[0035] In the first step, the stirring time may be, for example, 1 minute or more, 5 minutes or more, 15 minutes or more, 20 minutes or more, 30 minutes or more, or 60 minutes or more.

[0036] In one embodiment, in the second step, the hydrophilized inorganic fibers can be dispersed by stirring at a speed of 1,000 rpm or less for 5 minutes or more.

[0037] In the second step, the stirring speed may be, for example, 1,000 rpm or less, 800 rpm or less, 500 rpm or less, or 300 rpm or less.

[0038] In the second step, the stirring time may be, for example, 1 minute or more, 5 minutes or more, 15 minutes or more, 20 minutes or more, 30 minutes or more, or 60 minutes or more.

[0039] At this time, an impeller designed to minimize vortex generation can be applied to agitate the material, thereby dispersing and stabilizing the inorganic fibers.

[0040] In one embodiment, the wetting agent may be a cationic surfactant, an anionic surfactant, a nonionic surfactant, or a combination thereof.

[0041] For example, the wetting agent may be an EO (ethylene oxide) / PO (propylene oxide) copolymer surfactant, a PEO (polyethylene oxide)-based surfactant, a PEG (polyethylene glycol)-based surfactant, or a combination thereof.

[0042] In one embodiment, the copolymer may be contained in an amount of 0.1% to 10% by weight and the inorganic fibers in an amount of 0.01% to 10% by weight, based on a total content of 100% by weight of the inorganic fiber dispersion.

[0043] If the copolymer content exceeds the range, the viscosity of the dispersion increases, making dewatering and drying difficult during the production of the inorganic fiber wet nonwoven fabric. If the content falls below the range, the dispersion of fibers may decrease.

[0044] When creating the web, an appropriate content of the inorganic fibers can be selected according to the target basis weight. If the inorganic fiber content exceeds or falls below the specified range, frictional damage may increase or wetting may not be performed properly.

[0045] In one embodiment, the binder fibers may be present in an amount of 10% by weight or less, based on a total content of 100% by weight of the inorganic fiber dispersion.

[0046] If the binder fiber content exceeds the range described above, it may affect the formation of the interface between the thermoplastic fibers and inorganic fibers after the composite material is manufactured, potentially leading to a decrease in the physical properties of the composite material.

[0047] Furthermore, the wetting agent may be included in an amount of 0.01% by weight or more and 5% by weight or less, based on a total content of 100% by weight of the inorganic fiber dispersion.

[0048] In one embodiment, the ratio of moles of the acrylic acid monomer units to the acrylamide monomer units (moles of the acrylic acid monomer units:moles of the acrylamide monomer units) may be 10:90 to 90:10, based on a total copolymer content of 100 mol%.

[0049] For example, the mole percentage ratio of the acrylic acid monomer units to the acrylamide monomer units may be 90:10, 80:20, 70:30, 60:40, 50:50, 40:60, 30:70, 20:80, 10:90, or 30:70 to 70:30.

[0050] When using a homopolymer (a single polymer of acrylic acid or acrylamide) as a dispersant, inorganic fibers may not be properly dispersed.

[0051] In one embodiment, the monomer polymerized from the acrylic acid monomer units of the copolymer may be acrylic acid, methacrylic acid, itaconic acid, 2-acrylamido-2-methylpropane sulfonic acid, maleic acid, or a combination thereof.

[0052] Furthermore, the monomer polymerized from the acrylamide monomer units of the copolymer may be acrylamide, methacrylamide, or a combination thereof.

[0053] The copolymer may have a pH of 5 or higher and 10 or lower, and a viscosity of 100 cp or higher and 20,000 cp or lower.

[0054] For example, the pH of the copolymer may be 5 or higher and 9 or lower. If the pH of the inorganic fiber dispersion is above or below the above range, the dispersant may deteriorate over time, or the dispersion performance of the inorganic fibers may decrease.

[0055] The pH of the copolymer can be adjusted by adding alkali metals, alkaline earth metals, amine compounds, or combinations thereof.

[0056] In particular, the amine compound may be an amine compound with a pH of 9 or higher.

[0057] For example, sodium hydroxide, potassium hydroxide, ammonium hydroxide, lithium hydroxide, dimethylamine, trimethylamine, monoethanolamine, diethanolamine, triethanolamine, arginine, tromethamine, diisopropanolamine, and triisopropanolamine can be used to adjust the pH of the copolymer, but are not limited to these.

[0058] Furthermore, if the viscosity of the copolymer exceeds the aforementioned range, the viscosity may become too high, making it unsuitable for use. If it falls below this range, the inorganic fibers may not be properly dispersed.

[0059] On the other hand, the weight-average molecular weight of the copolymer may be 100,000 or more and 5,000,000 or less.

[0060] If the molecular weight of the copolymer exceeds the aforementioned range, its viscosity may be high, making it unsuitable for use. If it falls below this range, the inorganic fibers may not be properly dispersed.

[0061] Furthermore, depending on the molecular weight range, copolymers with low molecular weights can be suitable for short fiber dispersion, while copolymers with high molecular weights can be suitable for long fiber dispersion.

[0062] The inorganic fiber dispersion may have a pH of 2 or higher and 12 or lower, and a viscosity of 10 cp or higher and 200 cp or lower.

[0063] The third step is to form the inorganic fiber dispersion produced in the second step into an inorganic fiber wet nonwoven fabric shape by a wet process. For example, the inorganic fiber dispersion can be formed into an inorganic fiber wet nonwoven fabric shape using a wet-laid nonwoven fabric manufacturing machine, a hand-making machine, or the like.

[0064] For example, the third step involves distributing the inorganic fiber dispersion produced in the second step to a 25 × 25 cm 2 The process may include filtering the inorganic fiber dispersion using a hand-made papermaking machine and a mesh screen of 70 mesh to 130 mesh to produce paper, and then drying it in a hot-air drying oven at 90°C to 115°C for 50 to 70 minutes.

[0065] The filtration can use, for example, a mesh of 80 mesh to 110 mesh, 90 mesh to 100 mesh, or 100 mesh, and the drying may be carried out at, for example, 95°C to 110°C, 100°C to 110°C, or 105°C. Alternatively, the drying may be carried out in a hot air drying oven for 55 minutes to 65 minutes, 55 minutes to 60 minutes, or 60 minutes.

[0066] In one embodiment, the inorganic fiber may be a carbon fiber, a glass fiber, a basalt fiber, a ceramic fiber, a metal fiber, or a combination thereof.

[0067] In one embodiment, the thermoplastic fiber may be one or more selected from the group consisting of polyamide (PA), polyamide 6 (PA6), polyamide 6,6 (PA66), polyamide 12 (PA12), polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), polyether ether ketone (PEEK), polyethylene (PE), thermoplastic polyurethane (TPU), and polylactide (PLA), but is not limited thereto.

[0068] For example, the thermoplastic fiber may be polyamide 6 (PA6).

[0069] The thermoplastic fiber may be wrinkle-free (crimp-free).

[0070] In one embodiment, one or more of the inorganic fibers and thermoplastic fibers may include regenerated fibers.

[0071] For example, the regenerated thermoplastic fiber may be one or more selected from the group consisting of recycled polyamide (rPA), recycled polyamide 6 (rPA6), recycled polyamide 6,6 (rPA66), recycled polyamide 12 (rPA12), recycled polypropylene (rPP), recycled polyethylene terephthalate (rPET), recycled polybutylene terephthalate (rPBT), recycled polyphenylene sulfide (rPPS), recycled polyether ether ketone (rPEEK), recycled polyethylene (rPE), recycled thermoplastic polyurethane (rTPU), and recycled polylactide (rPLA), but is not limited thereto.

[0072] In one embodiment, the average length of the inorganic fibers may be 10 mm or more. For example, the average length of the inorganic fibers may be 12 mm or more, 24 mm or more, 36 mm or more, 48 mm or more, 50 mm or more, or 60 mm or more, but is not limited to these.

[0073] In one embodiment, the weight ratio of the inorganic fiber to the thermoplastic fiber may be 0.05:9.95 to 8:2. For example, it may be 0.1:9.9 to 7:3, 0.2:9.8 to 7:3, 0.5:9.5 to 7:3, 1:9 to 7:3, 1.5:8.5 to 7:3, 2:8 to 7:3, 2:8 to 7:3, 2.5:7.5 to 7:3, 3:7 to 7:3, 3:7 to 6:4, 3:7 to 5:5, 3.5:6.5 to 7:3, or 4:6 to 7:3.

[0074] In this case, if the weight ratio of the inorganic fibers falls below 0.05, the significance of the inorganic fiber composite material may diminish. On the other hand, if the weight ratio of the inorganic fibers exceeds 8, there is a limit to how much the thermoplastic fibers can melt and surround the inorganic fibers, resulting in a large number of voids in the inorganic fiber composite material. Furthermore, the density of the inorganic fiber composite material becomes very low, leading to a problem of reduced strength.

[0075] In one embodiment, the basis weight of the prepreg is 10 g / m². 2 More than 400g / m 2It may be as follows. For example, 10 g / m 2 or more, 100 g / m 2 or less, 100 g / m 2 or more, 200 g / m 2 or less, 200 g / m 2 or more, 400 g / m 2 or less, or 400 g / m 2 and may also be acceptable.

[0076] In one embodiment, the method for manufacturing the inorganic fiber composite material may additionally include a step of laminating one or more of the prepregs and heating and pressurizing them. The number of prepregs to be laminated may be, for example, one or more, three or more, or five or more.

[0077] The heating temperature may be 150°C or more and 350°C or less. For example, it may be 170°C or more and 330°C or less, 170°C or more and 310°C or less, 190°C or more and 300°C or less, 210°C or more and 290°C or less, 240°C or more and 260°C or less, 250°C or more and 350°C or less, or 250°C or more and 300°C or less.

[0078] The heating temperature may need to be a temperature that is equal to or higher than the melting point of the thermoplastic fibers in the one or more laminated prepregs and lower than the decomposition temperature.

[0079] The pressurizing pressure may be 0.5 MPa or more. For example, it may be 0.5 MPa or more, 1 MPa or more, 5 MPa or more, 10 MPa or more, or 20 MPa or more.

[0080] In one embodiment, the method for manufacturing the inorganic fiber composite material may include a step of laminating one or more of the prepregs, a forming step, a cooling step, a removing step, or a combination of these steps.

[0081] The forming step may include the step of heating and pressurizing.

[0082] The prepreg according to other embodiments of this application has a density of 0.3 g / cm³. 3 The following is also acceptable.

[0083] The prepreg refers to a single dried inorganic fiber wet nonwoven fabric produced by the steps of mixing the inorganic fiber and the thermoplastic fiber to produce an inorganic fiber wet nonwoven fabric, and drying the inorganic fiber wet nonwoven fabric to produce a prepreg.

[0084] For example, the density of the prepreg is 0.1 g / cm³. 3 Below 0.05g / cm 3 The following, or 0.001 g / cm³ 3 More than 0.006g / cm 3 The following is also acceptable.

[0085] On the other hand, the tensile strength of the prepreg may be 0.5 MPa or higher. For example, it may be 0.5 MPa or higher, 5 MPa or higher, 10 MPa or higher, 50 MPa or higher, 100 MPa or higher, 300 MPa or higher, or 500 MPa or higher.

[0086] Inorganic fiber composite materials according to yet another aspect of the present application may include the prepreg. The inorganic fiber composite material means one manufactured by laminating one or more prepregs and heating and pressurizing them. The inorganic fiber composite material may include one or more prepregs.

[0087] The inorganic fiber composite material has a density of 0.5 g / cm³. 3 It may be greater than this. For example, 0.75 g / cm³ 3 More than 1.0g / cm 3 More than 1.25g / cm 3 More than 1.5g / cm 3 Above, or 2.0 g / cm³ 3 That's fine too.

[0088] Furthermore, for example, if the inorganic fiber composite material contains four prepregs, the density is 0.5 g / cm³. 3 More than 2.0g / cm3 Below, 1.2g / cm 3 More than 1.55g / cm 3 Below, 1.2g / cm 3 More than 1.5g / cm 3 Below 1.25g / cm 3 More than 1.6g / cm 3 Below 1.25g / cm 3 More than 1.55g / cm 3 Below 1.25g / cm 3 More than 1.5g / cm 3 The following, or 1.28 g / cm³ 3 More than 1.45g / cm 3 The following is also acceptable.

[0089] The tensile strength of the inorganic fiber composite material may be 100 MPa or more. For example, it may be 230 MPa or more, 235 MPa or more, 240 MPa or more, 245 MPa or more, 250 MPa or more, 270 MPa or more, 290 MPa or more, or 320 MPa or more.

[0090] Furthermore, for example, if the inorganic fiber composite material includes four prepregs, the tensile strength may be 230 MPa or more, 400 MPa or less, 235 MPa or more, 420 MPa or less, 235 MPa or more, 400 MPa or less, 235 MPa or more, 395 MPa or less, 240 MPa or more, 395 MPa or less, 245 MPa or more, 395 MPa or less, or 245 MPa or more, 420 MPa or less.

[0091] The bending strength of the inorganic fiber composite material may be 150 MPa or more. For example, it may be 350 MPa or more, 360 MPa or more, 370 MPa or more, 380 MPa or more, 390 MPa or more, 400 MPa or more, or 450 MPa or more.

[0092] Furthermore, for example, if the inorganic fiber composite material includes four prepregs, the bending strength may be 350 MPa or more, 620 MPa or less, 350 MPa or more, 610 MPa or less, 350 MPa or more, 600 MPa or less, 360 MPa or more, 620 MPa or less, 370 MPa or more, 620 MPa or less, 380 MPa or more, 630 MPa or less, 380 MPa or more, 620 MPa or less, 385 MPa or more, 600 MPa or less, 400 MPa or more, 600 MPa or less, or 385 MPa or more, 585 MPa or less.

[0093] In one embodiment, the electromagnetic shielding of the inorganic fiber composite material may be 35 dB or more. For example, it may be 37 dB or more, 40 dB or more, 50 dB or more, 60 dB or more, or 70 dB or more.

[0094] The electromagnetic shielding of the inorganic fiber composite material may be a measured value when the inorganic fibers are manufactured using carbon fibers, metal fibers, or a combination thereof.

[0095] Furthermore, for example, if the inorganic fiber composite material includes four prepregs, the electromagnetic wave shielding may be 35 dB or more, 70 dB or less, 35 dB or more, 68 dB or less, 37 dB or more, 75 dB or less, 37 dB or more, 70 dB or less, 37 dB or more, 68 dB or less, 40 dB or more, 75 dB or less, 40 dB or more, 70 dB or less, 50 dB or more, 70 dB or less, or 40 dB or more, 68 dB or less. [Examples]

[0096] The present application will be described in more detail below using examples, but the application is not limited thereto.

[0097] Manufacturing Example 1. Production of Carbon Fiber Dispersion Based on a total content of 500g, carbon fiber (Zolteck), polyamide 6 (PA6) fiber (Nylon 6, Toray), and a nonionic surfactant-based wetting agent were mixed in the remaining solvent (water) after adjusting the content as shown in Table 1 below. Then, a pulper was applied and a pre-wetting step (a step to produce a solution containing hydrophilized carbon fiber) was performed at 1,250 rpm for 5 minutes.

[0098] Subsequently, 500 g of the solution containing the hydrophilized carbon fibers that had undergone the pre-wetting step was added to a polymer (dispersant) solution prepared by dissolving 3,950 g of solvent (water) and 50 g of acrylic copolymer (dispersant). An impeller designed to minimize vortex formation was applied, and the mixture was stirred at a low speed of 300 rpm or less for 10 minutes to produce the carbon fiber dispersions of Examples 1 to 3.

[0099] The average length of the carbon fibers used was 12 mm.

[0100] The average length and content of the carbon fibers used, the content of PA fibers (polyamide 6), and the content of the wetting agent are shown in Table 1 below.

[0101] [Table 1]

[0102] Manufacturing Example 2. Prepreg Manufacturing 25 x 25 cm 2 Using a hand-made papermaking machine and a 100-mesh screen, paper was made from the carbon fiber dispersions of Examples 1-3. This was then dried in a hot air drying oven at 105°C for 1 hour to produce a prepreg (wet-laid carbon fiber nonwoven fabric).

[0103] Using the carbon fiber dispersions from Examples 1-3, a basis weight of 320 g / m² was produced according to Production Example 2. 2 , size 25 x 25 cm 2 The density and tensile strength of the prepreg were measured.

[0104] The density of the prepreg was calculated after measuring its weight and thickness.

[0105] The tensile strength of the prepreg was measured at a speed of 2 m / min using Shimadzu's AGS-X 10N-10KN device, in accordance with the ASTM D3039 / D3039M-17 test standard.

[0106] The measured density and tensile strength of the prepreg are shown in Table 2 below.

[0107] Manufacturing Example 3. Manufacturing of Carbon Fiber Composite Materials Four prepregs manufactured according to Manufacturing Example 2 were stacked, heated at 250°C for 10 minutes, and then pressurized at 10 MPa to produce a carbon fiber composite material.

[0108] The density, tensile strength, flexural strength, and electromagnetic shielding properties of the carbon fiber composite material manufactured according to Manufacturing Example 3 were measured.

[0109] The tensile strength of the carbon fiber composite material was measured according to the ASTM D3039 / D3039M-17 test standard.

[0110] The flexural strength of the carbon fiber composite material was measured according to the ASTM D790-17 test standard.

[0111] The electromagnetic shielding of carbon fiber composite materials was measured according to the ASTM D4935-10 test standard.

[0112] The measured density, tensile strength, flexural strength, and electromagnetic shielding of the carbon fiber composite material are shown in Table 2 below.

[0113] [Table 2]

[0114] When comparing prepregs produced using the carbon fiber dispersions of Examples 1-3 according to Production Example 2, it was confirmed that the tensile strength was improved when the weight ratio of carbon fiber to PA fiber was 5:5 (Examples 2 and 3) compared to when it was 3:7 (Example 1).

[0115] In particular, when using the carbon fiber dispersions of Examples 2 and 3, in which the weight ratio of carbon fiber to PA fiber was 5:5, we were able to confirm that the tensile strength improved as the carbon fiber content increased in the prepreg produced by Production Example 2.

[0116] When using the carbon fiber dispersions of Examples 1-3, the density values ​​of the prepregs produced according to Production Example 2 did not differ significantly.

[0117] Furthermore, when comparing the carbon fiber composite material produced using the carbon fiber dispersions of Examples 1-3 with the prepreg produced using the carbon fiber dispersions of Examples 2, it was confirmed that the density and tensile strength were significantly improved.

[0118] In particular, when comparing Examples 1-3 with the carbon fiber dispersions used to produce the carbon fiber composite material manufactured according to Production Example 3, it was confirmed that when the weight ratio of carbon fiber to PA fiber was 5:5 (Examples 2 and 3), density, tensile strength, bending strength, and electromagnetic shielding were all improved compared to when the weight ratio was 3:7 (Example 1).

[0119] Furthermore, using the carbon fiber dispersions of Examples 2 and 3, where the weight ratio of carbon fiber to PA fiber was 5:5, it was confirmed that in the case of the carbon fiber composite material produced by Production Example 3, density, tensile strength, bending strength, and electromagnetic shielding all improved as the carbon fiber content increased.

[0120] In other words, it was confirmed that the physical properties (density, tensile strength, flexural strength, and electromagnetic shielding) of the carbon fiber prepreg and carbon fiber composite material mixed with carbon fiber according to the present application have similar tendencies.

[0121] Furthermore, it was confirmed that the prepreg and carbon fiber composite material obtained by mixing carbon fibers and thermoplastic fibers in this application possess excellent physical properties despite using carbon fibers with a relatively long average length of 12 mm.

[0122] In addition, we have confirmed that the prepreg and carbon fiber composite materials of this application, compared to existing prepreg and carbon fiber composite materials, can simplify the manufacturing process by prioritizing the process of mixing carbon fibers and thermoplastic fibers to produce a carbon wet nonwoven fabric, without the need for a solution impregnation or hot melt process, thereby ensuring prepreg and carbon fiber composite materials with excellent physical properties.

[0123] The scope of the present invention is defined by the claims set forth below rather than by the detailed description above, and all modifications or alterations derived from the meaning and scope of the claims and the concept of equivalents thereof should be interpreted as being included within the scope of the present invention.

Claims

1. A step of mixing inorganic fibers and thermoplastic fibers to produce an inorganic fiber wet nonwoven fabric, The process includes the step of drying the inorganic fiber wet nonwoven fabric to produce a prepreg. A method for manufacturing inorganic fiber composite materials.

2. The inorganic fibers are carbon fibers, glass fibers, basalt fibers, ceramic fibers, metal fibers, or a combination thereof. A method for producing an inorganic fiber composite material according to claim 1.

3. The thermoplastic fiber is one or more selected from the group consisting of polyamide (PA), polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), polyether ether ketone (PEEK), polyethylene (PE), thermoplastic polyurethane (TPU), and polylactide (PLA). A method for producing an inorganic fiber composite material according to claim 1.

4. One or more of the inorganic fibers and thermoplastic fibers include regenerated fibers. A method for producing an inorganic fiber composite material according to claim 1.

5. The average length of the inorganic fibers is 10 mm or more. A method for producing an inorganic fiber composite material according to claim 1.

6. The weight ratio of the inorganic fiber to the thermoplastic fiber is 0.05:9.95 to 8:

2. A method for producing an inorganic fiber composite material according to claim 1.

7. The basis weight of the prepreg is 10 g / m². 2 Above, 400g / m 2 The following is: A method for producing an inorganic fiber composite material according to claim 1.

8. The additional step includes stacking one or more of the aforementioned prepregs, heating them, and pressurizing them. A method for producing an inorganic fiber composite material according to claim 1.

9. The heating temperature is 150°C or higher and 350°C or lower. The pressure of the aforementioned pressurization is 0.5 MPa or higher. A method for producing an inorganic fiber composite material according to claim 8.

10. The density is 0.3 g / cm³. 3 The following is: Prepreg.

11. The prepreg includes the one described in claim 10. Inorganic fiber composite material.

12. The electromagnetic shielding is 35 dB or higher. The inorganic fiber composite material according to claim 11.

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